In such conventional servo-operated curtains, the controllable drive mechanism--as a rule an electric motor--works on a curtain cord, which is secured to a curtain ring which is adjacent to the free curtain end. Such servo controls are, however, susceptible to trouble.
The present invention is a further development of a servo control mechanism in such a manner that a higher operating safety is achieved.
Starting out from the state of the art, this purpose is inventively attained by providing a servo control mechanism for a curtain supported by a curtain rod through at least one curtain ring, which servo control mechanism has a controllable drive means operating on the curtain ring. The curtain rod is of a tubular construction and is made of a nonmagnetizable material. A piston is movably supported inside the curtain rod with opposite sides thereof being selectively supplied with pressurized fluid. An elongated strand effects a coupling of the piston to at least one permanent magnet also movably mounted inside the curtain rod. The curtain ring surrounds the curtain rod and is made of a magnetizable material and, consequently, is magnetically coupled to the permanent magnet inside the curtain rod. If more than one ring is used, only certain ones of the rings are made of magnetizable material and the number of permanent magnets equals the number of such rings.
The inventive servo control mechanism has the further advantage that it is totally out of the sight of the viewer. It moreover also operates practically without any sound, is service free, and the closing and opening speed of the curtain can be varied simply by a suitable control of the pressure, with which the piston which runs in the curtain rod is loaded. The inventive servo control consists of mechanically simple parts and can thus be produced inexpensively and can be easily installed. It can also be used easily in rooms, where otherwise special, explosion-protected electrical systems would have to be used.
Since two magnets are directly connected to opposite sides of the piston, they can take over the guiding task and the piston can thus be optimized with respect to its sealing function.
In addition, it is achieved that in the case of a possible tilting of the magnets, a jamming in the curtain rod is not possible, since the effective cross section remains the same.